SNC 2D

The Nervous System

The organ system that is made up of the brain, spinal cord, and the peripheral nervesSystem that senses the environment and coordinates appropriate responses

Nervous System

Consists of the brain and the spinal cord

Shielded by bonesSkull protects the brainSpine protects the spinal cord

Cerebrospinal fluid surrounds the brain and spinal cord – cushions against injury and transports chemicals and waste

Central Nervous System

Consists of the nerves that connect the body to the central nervous system

Relays information about the internal and external environments of the brain

Subdivided into A) nerves that control voluntary musclesB) nerves that carry information from sensory

organsC) nerves that regulate involuntary functions

Peripheral Nervous System

Specialized cells that make up nerve tissue are called neurons

Found in brain, spinal cord and nervesApproximately 100 billion neurons in human

brain

Neurons conduct electrical signals (nerve impulses) from one area of body to another

Nerve Tissue

Structure

Nerve cell sends a signal through axonAttaches to dendrites of another cellContinues until reaches muscle cellsSignal goes in only one direction

Sending a Signal

Fatty material that surrounds the axonActs like an electrical wire preventing

electrical impulses from passing to the wrong neuron

Myelin Sheath

Bundles of neurons surrounded by connective tissueAllow two-way flow of information even though each neuron transmits information only in one direction

Nerves

Special cells or tissues that receive input from our external environment and send signals along our peripheral nerves to our central nervous system

Ears, mouth, nose, muscles, and skinOther receptors are sensitive to pressure, temperature, and pain and make us aware of our balance, position and motion

Sensory Receptors

Increase/decrease breathing rateHeart beat faster/slowerEat/drink/stopPerception

Spinal Cord – acts as a short cut for reflexesReflexes do not use brain, occur without

conscious thought (move hand away from hot surface)

Other functions

Peripheral nervous system can undergo cell division to repair severed nerves (few mm distance)

Central nervous system do not regenerate easily

Repair

Multiple Sclerosis – destroys myelin sheaths so that signals are mixed up

Fall or blow – can result in paralysis, concussions

Viruses and bacteria can cause permanent damage in brain

nervous systempork tapeworm

Diseases and Disorders